The present invention relates to the field of remote powering and more particularly to a power over Ethernet controller supporting high power over both two twisted wire pairs and four twisted wire pairs.
The growth of local and wide area networks based on Ethernet technology has been an important driver for cabling offices and homes with structured cabling systems having multiple twisted wire pairs. The ubiquitous local area network, and the equipment which operates thereon, has led to a situation where there is often a need to attach a network operated device for which power is to be advantageously supplied by the network over the network wiring. Supplying power over the network wiring has many advantages including, but not limited to; reduced cost of installation; centralized power and power backup; and centralized security and management.
Several patents addressed to this issue exist including: U.S. Pat. No. 6,473,608 issued to Lehr et al., and U.S. Pat. No. 6,643,566 issued to Lehr et al., the entire contents of both of which are incorporated herein by reference. Furthermore a standard addressed to the issue of powering remote devices over an Ethernet based network, known as Power over Ethernet (PoE), has been published as IEEE 802.3af-2003, whose contents are incorporated herein by reference.
The above standard is limited to a powered device (PD) having a maximum power requirement during operation of 12.95 watts. Power can be delivered to the PD either directly from the switch/hub known as an endpoint power sourcing equipment (PSE) or alternatively via a midspan PSE. Unfortunately, no provision has been made in the above standard for PDs requiring power in excess of the above maximum power requirement. The above power limitation is primarily a function of the power carrying capabilities of the installed twisted wire pairs being utilized to deliver power.
Each port in a PoE system supplies power to a connected PD, with power being transmitted from the port to the PD over two twisted wire pairs of the structured communication cabling. For each group of ports to be powered, a control circuit is typically provided to accomplish detection, optional classification, powering and monitoring in accordance with the above standard. For example, the PD64004 is a 4 channel PoE manager commercially available from PowerDsine, Ltd. of Hod Hasharon, Israel. The PD64004 implements all real time activities according to the IEEE 802.3af standard, including: detection, classification, and port status monitoring; as well as system level activities such as power management and data support for system PoE management. The PD64004 is designed to detect and disable disconnected ports, using both DC and AC disconnection methods, as defined in the aforementioned standard. The term PoE manager and PoE controller are used interchangeably throughout this document.
As described above, the current IEEE 802.3af-2003 standard is limited to a PD consuming 12.95 watts, and thus PoE controllers are designed to support these power levels. Co-pending U.S. patent application Ser. No. 10/761,327 filed Jan. 22, 2004 and published on Apr. 21, 2005 as US2005/0085212A1, the entire contents of which are incorporated herein by reference, is addressed to high power PDs requiring in excess of 12.95 watts. Power is provided over four twisted wire pairs and combined at the high power PD. Preferably power is provided simultaneously over all four twisted wire pairs. Unfortunately, commercially available PoE controllers, such as the one described above, are not designed to support such an architecture.
It has been further proposed that power in excess of the 12.95 watt limit can be supported by two twisted wire pairs of the existing communication cabling. Such an increased power will however be in excess of the design constraints of many of today's integrated PoE controllers, which exhibit integrated switches having thermal constraints.
What is therefore needed, and not known in the prior art, is a PoE controller capable of supporting powering according to the aforementioned standard, and further supporting both increased power levels over two twisted wire pairs and four twisted wire pairs.